Matchmaking question: Why do some games seem unfair?

I play normals only. Too often lately, the games I had are like: 3-4 players of my skill level and 2-1 players playing a bit worse (but still knowing what he has to do) on the enemy team, and 3 (always) players playing worse than me and only one reasonable man but usually flames a lot. I tend to have like 10 of such games a week, and only one game where everyone seems to know what they must do, probably with higher skill than me and the losses are usually because of either me or someone on the other team doing something stupid. The reliance on one single player in the first case, in a game in which teamwork is all, makes me question matchmaker's decisions all the time. I can be a captain, I can lead my whole team, but can't I have some fun at least once or twice. Why me picking urgot top results in a BIG decrease of my winrate, note that I consider myself being not the worst urgot in the world. I have like 80 difference in win/loss (more wins than losses). But it has become incredibly tiring to tryhard all the time. What's your advice for me and possible explanation for this phenomena?